As Bmrox' wrote, the center part is a resonator. A lot of people on the US forums delete the resonator when fitting an aftermaket muffler. I'm not really sure if there may be a risk of drone or resonance at certain RPM levels, since the resonator is there for that kind of reason.

I found a pic of the front cat on my car. It is part of the exhaust header and is right next the the steering shaft. You won't see it unless you are fully under the car, or otherwise point your camera in the right direction like I did.